:root{--paper:#f5faf7;--ink:#143e31;--muted:#466357;--accent:#176247;--line:#c8dbd0;--card:#fff;--soft:#e6f3eb;color-scheme:light}
*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;font-size:18px;line-height:1.7}
body.game{--paper:#f4f0e7;--ink:#24211c;--muted:#625c51;--accent:#a32920;--line:#cfc6b7;--soft:#e9e1d3;font-family:Georgia,"Times New Roman",serif}
a{color:var(--accent);text-underline-offset:3px}a:hover{text-decoration-thickness:2px}a:focus-visible,button:focus-visible,summary:focus-visible,input:focus-visible{outline:3px solid var(--accent);outline-offset:4px}
.learn-header{max-width:1120px;margin:auto;padding:24px;display:flex;align-items:center;justify-content:space-between;gap:24px;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:12px;font-weight:750;text-decoration:none;color:var(--ink)}.brand img{width:42px;height:42px;border-radius:10px}nav{display:flex;flex-wrap:wrap;gap:22px;font-size:15px;font-family:system-ui,sans-serif}nav a{color:var(--ink)}
main{min-height:60vh}article{max-width:820px;margin:0 auto;padding:52px 24px 64px}h1,h2,h3{line-height:1.2;letter-spacing:-.025em}h1{font-size:clamp(34px,5vw,54px);margin:20px 0 24px}h2{font-size:28px;margin:44px 0 18px}h3{font-size:22px;margin:32px 0 12px}p{margin:0 0 20px}.lead{font-size:21px;line-height:1.6;color:var(--muted);margin-bottom:36px}.breadcrumb,.eyebrow{font-family:system-ui,sans-serif;font-size:14px;font-weight:650}li{margin-bottom:10px}strong{font-weight:700}
table{display:block;max-width:100%;overflow-x:auto;border-collapse:collapse;margin:24px 0 30px;font-family:system-ui,sans-serif;font-size:16px}caption{text-align:left;font-weight:700;padding:0 0 12px;color:var(--ink)}th,td{text-align:left;padding:12px 14px;border:1px solid var(--line);vertical-align:top}th{background:var(--soft)}tbody{background:var(--card)}td:first-child{font-size:20px}details{padding:16px 20px;border:1px solid var(--line);border-radius:8px;margin:18px 0;background:var(--card)}summary{cursor:pointer;font-weight:650}details[open] summary{margin-bottom:14px}details p:last-child{margin-bottom:0}
.app-cta{display:flex;align-items:flex-start;gap:20px;padding:28px;margin:48px 0;background:var(--soft);border:1px solid var(--line);border-radius:12px}.app-cta img{width:66px;height:66px;border-radius:15px}.app-cta h2{margin:0 0 12px;font-size:24px}.download,button{display:inline-block;background:var(--accent);color:white;border:1px solid var(--accent);border-radius:7px;padding:12px 18px;font:650 16px/1.45 system-ui,sans-serif;text-decoration:none;cursor:pointer}.download:hover,button:hover{filter:brightness(.92)}.secondary{background:transparent;color:var(--accent)}.sources{font-size:15px}.related li{margin-bottom:12px}
.guide-index{max-width:1120px;margin:auto;padding:48px 24px 64px}.guide-index .lead{max-width:740px}.guide-grid{list-style:none;padding:0;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.guide-grid li{margin:0}.guide-grid a{display:block;height:100%;padding:26px;border:1px solid var(--line);border-radius:12px;background:var(--card);text-decoration:none}.guide-grid h2{margin:0 0 14px;font-size:25px;color:var(--ink)}.guide-grid p{font-size:16px;color:var(--muted)}.guide-grid span{font-size:15px;font-weight:700}
.practice-quiz{padding:24px;background:var(--soft);border-radius:12px;border:1px solid var(--line)}fieldset{margin:26px 0;padding:20px;border:1px solid var(--line);border-radius:8px;background:var(--card);min-width:0}legend{padding:0 6px;font-weight:650;line-height:1.5}.question-number{display:block;font-size:13px;color:var(--muted)}.glyph{font-size:46px;font-family:"PingFang SC","Noto Sans CJK SC","Microsoft YaHei",sans-serif;line-height:1.4;font-weight:400}.choices{display:grid;grid-template-columns:1fr 1fr;gap:10px}.choices label{display:flex;align-items:center;gap:8px;padding:12px;border:1px solid var(--line);border-radius:6px;cursor:pointer;font-size:16px}.choices input{width:18px;height:18px;accent-color:var(--accent)}.feedback{font-size:16px;margin:16px 0 0}.answer-key{font-size:15px}.practice-actions{display:flex;flex-wrap:wrap;gap:12px;margin:22px 0}.quiz-result{font-weight:650;margin:20px 0 0}.card-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.flashcard{margin:0;text-align:center;padding:18px 12px}.flashcard summary{display:flex;flex-direction:column;align-items:center;font-size:13px;min-height:96px;justify-content:center}.flashcard summary::-webkit-details-marker{display:none}.flashcard .glyph{font-size:56px}.card-answer{display:flex;flex-direction:column;gap:4px;font-size:16px}.card-answer span[lang]{font-size:23px}
footer{max-width:1120px;margin:auto;border-top:1px solid var(--line);padding:28px 24px;font-size:14px;display:flex;flex-wrap:wrap;gap:18px;font-family:system-ui,sans-serif}footer p{width:100%;color:var(--muted);margin:0}.skip{position:fixed;left:10px;top:-100px;padding:12px;background:white;z-index:5}.skip:focus{top:10px}[hidden]{display:none!important}
@media(max-width:600px){body{font-size:17px}.learn-header{padding:18px;flex-direction:column;align-items:flex-start;gap:16px}nav{gap:20px}.guide-grid{grid-template-columns:1fr}article,.guide-index{padding:32px 18px 48px}.app-cta{padding:20px;gap:12px;flex-direction:column}.card-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.practice-quiz{padding:14px}fieldset{padding:14px}.choices{grid-template-columns:1fr}h2{font-size:25px}.lead{font-size:19px}}
@media print{body{background:white;color:black;font-size:12pt}.learn-header,footer,.app-cta,.related,.sources,.practice-actions,.breadcrumb,.skip{display:none!important}article{max-width:none;padding:0}.flashcards .card-grid{grid-template-columns:repeat(3,1fr)}.flashcard{break-inside:avoid}.flashcard .card-answer{display:flex!important}.flashcard summary span:last-child{display:none}details{break-inside:avoid}table{overflow:visible}a{color:black}}